Wilmington Taps Honeywell for $35m Biogas Capture and Thermal Drying

September 13, 2012 By Paul Nastu

Honeywell is to complete a $35 million renewable energy project for the city of Wilmington, Del., which will feature a first-of-its-kind facility that converts two sources of biogas into power and heat for the city’s wastewater treatment plant.

The project is part of a city-wide initiative to decrease energy costs and greenhouse gas emissions, a program that has also included Honeywell-led solar installations and energy-efficient building improvements. Combined, the upgrades will help the city trim its carbon footprint by about 35 percent and meet nearly 50 percent of its electricity needs with renewable energy, Honeywell says.
City officials intend to use the subsequent reduction in utility and operating costs, savings that are guaranteed through performance contracts with Honeywell, to fund the upgrades and ongoing support. In addition, the work is expected to deliver savings beyond the money required to finance the activities.

The centerpiece of the new project is the construction of a renewable energy biosolids facility to harvest biogas, supplying a renewable resource to not only generate electricity for the Hay Road Wastewater Treatment Plant, but provide thermal drying to greatly reduce the volume of sewage sludge the city pays to remove.

The biosolids facility will capture methane produced by anaerobic digesters at the Hay Road plant, harnessing a potential energy source that is currently flared off. The gas will mix with additional methane from the nearby Cherry Island Landfill, which is operated by the Delaware Solid Waste Authority. The blend will be purified and used to power reciprocating engines that can generate up to 4 MW of electricity, enough to provide up to 90 percent of the treatment plant’s power.

The biosolids, or sewage sludge, that come out of the digesters will also be dehydrated by heat recovered from the engines. This thermal drying process is expected to reduce the amount of sludge the city needs to truck away by about 75 percent — from 140 to 35 tons per day — greatly reducing material-handling costs. It should also trim greenhouse gas emissions by 15,700 metric tons annually, Honeywell says.

In February, energy efficiency and renewable energy company Ameresco and the Philadelphia Water Department announced plans to design, build and maintain a wastewater biogas-to-energy facility. The $47.5 million construction project is expected to generate 5.6 MW of power and reduce PWD’s energy costs by over $12 million over the course of the 16-year contract.

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